13 111.-On Titanic Acid. BY E. RILEY,F.C.S TIT-4NIC acid from its great similarity to sihcic acid is frequently overlooked in the analyses of silicates although it occurs in many instances in some quantity. The properties of the two acids being so similar there arises great difficulty in separating them ; moreover the ordinary test for minute quantities of titanic acicl is unsatisfactory ; and it became necessary before commencing ex- periments on the subject to see if some better test than the ordinary one with microcosmic salt in the reducing flame of the blow-pipe either alone or with the addition of tin could not be suggested. It occurred to me from the remark made by Karsten viz. “That muffles made of Cracow clay used for the distillation of zinc assume a blue co1our”-that some reaction with this metal might be made available as a test for the acid.In trying zinc in various ways it was found when this metal was used in the reducing flame of the blow-pipe in the metallic state in conjunction with minute quantities of titanic acid that after the combustion of the zinc and clearing of the bead on cooling a very distinct coloration was always produced whereas the button of microcosmic salt and titanic acid being tried pre- viously in the ordinary way gave no reaction. By this test titanic acid may be found in pig iron and in most cases where any residue is left by treating silica with hydrofluoric acid. In the determination of silica (in the ordinary way by fusion with carbonate of soda) in several samples of fire-bricks it was always found that there was a considerable residue left after treat- ing the silica with hydrofluoric acid in Rrunner’s apparatus This residue consisting of a fluoride of titanium with possibly some titanic acid cannot be heated without the fluoride of titanium being volatilized; in fact by far the larger portion of it goes off.An experiment made on 2.235 grains of titanic acid exposed for some twenty-four hours (with the occasional addition of water) in Brunner’s apparatus until it was completely dissolved left on evaporating to dryness and beating carefully to a low red heat only a residue of -99 grains which still contained a trace of fluorine; hence it follows that the residues obtained by the same method as IiILEY ON TITANIC ACID.detailed in the above experiment from the silica of the fire-bricks represents only a portion of the titanic acid actually present. After the separation of the silica in these analyses the filtrate mas again evaporated to dryness and heated. A residue mas then obtained which was at first considered to be silica not having been rendered insoluble by the first heating. Through the whole series of analyses however in several cases of which the fusion after evaporating to dryness was subjected to very various temperatures some extending over a long time and heated to a high tempera- ture on a porcelain dish a residue was always obtained on evapo- rating the filtrate from the silica to dryness as will be seen from the table appended :- ~~~ ~~~ ~ Number.Weight of Fire-brick taken. Silica ob- tained. Residue on second evaporation Residue from Silica by HFI. Second evapo-ration. Resi- dueby HP1. 1 2 17.42 18.25 3 0.77 11.925 I *325 -41 -19' *22 -1 1 3 18.41 11.435 -42 -226 -07 4 17.74 10.41 1.115t *236 5 18-08 11.79 -39 ,135 -16 6 7 17-45 18.21 10.04 10.64 -375 -435 *13 -17 ,115 -11 8 18.325 10 325 -34 -165 -09 9 18.43 1116 .36 -19 -095 10 18.10 10.22 -34 *I9 *13 11 18-34 11-175 -41 -14 .13 Mean of 9 18.17 10.98 -386 .174 -112 The residue in column 4 had all the characteristics of titanic acid although it probably contains a small amount of silica; when heated it assumed the yellow tint of titanic acid and the residue left after heating with hydrofluoric acid shows that a large pro- portion of it was titanic acid. It may be mentioned that these residues were tested for alumina; only a trace was found. * Silica and residue on second evaporation added together and heated with HPI. + Some silica passed through filter in first filtration; both added together as in number one and treated with hydrofluoric acid.